distmatrix.m

较简单的KMeans聚类算法实现

function d=DistMatrix(A,B)
             %%%%%%%%%%%%%%%%%%%%%%%%%
             % DISTMATRIX return distance matrix between points in A=[x1 y1 ... w1] and in B=[x2 y2 ... w2]
             % Copyright (c) 2005 by Kardi Teknomo,  http://people.revoledu.com/kardi/
             %
             % Numbers of rows (represent points) in A and B are not necessarily the same.
             % It can be use for distance-in-a-slice (Spacing) or distance-between-slice (Headway),
             %
             % A and B must contain the same number of columns (represent variables of n dimensions),
             % first column is the X coordinates, second column is the Y coordinates, and so on.
             % The distance matrix is distance between points in A as rows
             % and points in B as columns.
             % example: Spacing= dist(A,A)
             % Headway = dist(A,B), with hA ~= hB or hA=hB
             %          A=[1 2 3; 4 5 6; 2 4 6; 1 2 3]; B=[4 5 1; 6 2 0]   
             %          dist(A,B)= [ 4.69   5.83;            
             %                       5.00   7.00;           
             %                       5.48   7.48;            
             %                       4.69   5.83]            
             %            
             %          dist(B,A)= [ 4.69   5.00     5.48    4.69;        
             %                       5.83   7.00     7.48    5.83]        
             %%%%%%%%%%%%%%%%%%%%%%%%%%%
             [hA,wA]=size(A);            
             [hB,wB]=size(B);            
             if wA ~= wB,  error(' second dimension of A and B must be the same'); 
             end
             for k=1:wA                  
                 C{k}= repmat(A(:,k),1,hB);                
                 D{k}= repmat(B(:,k),1,hA);            
             end
             S=zeros(hA,hB);
             for k=1:wA                  
                 S=S+(C{k}-D{k}').^2;          
             end
             d=sqrt(S);